In the field of refrigeration and air conditioning, 1,1,1,2-tetrafluoroethane (R134a) that is a hydrofluorocarbon (HFC) and R410A that is a mixed refrigerant of difluoromethane (R32) and pentafluoroethane (R125) in a mass ratio of 1/1 are currently widely used as refrigerants for a refrigerator, a car air conditioner, a room air conditioner, industrial refrigerating machine, and the like. Although such HFC refrigerants have an ozone depletion potential (ODP) of zero, they have a high global warming potential (GWP) of 1000 or more, and therefore, their usage is limited in accordance with what is called the F-gas regulations aiming at the global environmental protection.
As an alternative for a refrigerant having a high GWP, tetrafluoropropene is under examination as a candidate owing to its thermodynamic characteristic. Since 2,3,3,3-tetrafluoropropene (HFO-1234yf) has a GWP as low as 4, it is under examination as a potential candidate.
With respect to a base oil for a general industrial lubricating oil, Patent Literature 1 proposes a lubricating oil base oil containing a synthetic ester obtained by reacting an alcohol component containing 90% by mass or more of trimethylolpropane with a carboxylic acid component that contains a monocarboxylic fatty acid having 8 to 12 carbon atoms and adipic acid, and further contains, in a total amount of 90% by mass or more, caprylic acid and/or a monocarboxylic fatty acid having 8 to 12 carbon atoms containing 90% by mass or more of caprylic acid in total, and adipic acid.